<SUBMISSION>
<ACCESSION-NUMBER>0001180472-06-000003
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20060221
<FILING-DATE>20060222
<DATE-OF-FILING-DATE-CHANGE>20060222
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>KNOLL JEROME C
<CIK>0001180472
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-32729
<FILM-NUMBER>06635479
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>5098351512
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>601 W RIVERSIDE AVE SUITE 1100
<CITY>SPOKANE
<STATE>WA
<ZIP>99201
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>POTLATCH CORP
<CIK>0001338749
<ASSIGNED-SIC>6798
<IRS-NUMBER>820156045
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>601 WEST RIVERSIDE AVENUE
<STREET2>SUITE 1100
<CITY>SPOKANE
<STATE>WA
<ZIP>99201
<PHONE>(509) 835-1500
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>601 WEST RIVERSIDE AVENUE
<STREET2>SUITE 1100
<CITY>SPOKANE
<STATE>WA
<ZIP>99201
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>Potlatch Holdings, Inc.
<DATE-CHANGED>20050914
</FORMER-COMPANY>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-02-21</periodOfReport>

    <issuer>
        <issuerCik>0001338749</issuerCik>
        <issuerName>POTLATCH CORP</issuerName>
        <issuerTradingSymbol>PCH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001180472</rptOwnerCik>
            <rptOwnerName>KNOLL JEROME C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>601 W. RIVERSIDE AVENUE, SUITE 1100</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SPOKANE</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>99201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-02-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1879</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>22.0713</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12064</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>22.0713</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-02-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1879</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-12-04</value>
            </exerciseDate>
            <expirationDate>
                <value>2013-12-04</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1879</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person was granted stock options on December 4, 2003, to vest in two equal annual installments.  The reporting person previously exercised the first installment and this figure represents the second installment exercised.  The grant was made under the stockholder-approved Potlatch Corporation 2000 Stock Incentive Plan.</footnote>
        <footnote id="F2">The stock option, after exercise, was acquired and added to the shares previously owned by the reporting person, therefore Column 8 has been left blank.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Malcolm A. Ryerse, Attorney-in-fact</signatureName>
        <signatureDate>2006-02-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
